Transmission problem. Mazda Protege 1999 Auto 1.6L
 

Mazda Protege 1999 Auto 1.6L 200,000 km
Car runs ok when the engine is cold. The problem happens after the engine reaches the operating temperature. When taking off after stopping for lights the car is sluggish. The RPM goes to 5000 but the car moves slowly.

Could you tell where the problem is?

I want to repair a second hand transmission which I have bought and replace the troubled one. I have the second-hand transmission dismantled. I want to find if any problem exists before fitting.

Which areas inside the transmission, I have to check ?

Thanks in advance for your reply